Is the supplementary certificate of flexible employment valid for social security?

It's useless According to the inquiry of Social Insurance Law of People's Republic of China (PRC), since March 18, 2022, it is illegal for flexible employees to attach themselves to social security laws and regulations, which harms the public interests, and the social security of the parties concerned will also be cancelled and invalid. Social insurance is a social and economic system that provides income or compensation for those who lose their ability to work, are temporarily unemployed or suffer losses due to health reasons.